Electrical transformer construction



May 1, 1928. 1,668,110

J. FISCHER ELECTRI CAL TRANSFORMER C ONSTHUCTION Filed Feb. 27. 1926 Patented May 1, 1928.

UNITED STATES PATENT oFFicE.

JOSE! FISCHER, OF BADEN, SWITZERLAND, ABSIGNOB TO AKTIEE'GESELLSCHAH BROWN BO'V'ERI 8t CIR, 0F BADEN, SWITZERLAND, A JOINT-STOCK COMPANY 01 SWITZERLAND.

ELECTRICAL TRANSFORMER CONSTRUCTION.

Application filed February 27, 1926, Serial No- 9 ,00 and in Germany larch 9, 1988.

This invention relates to construction of electrical transformers, and finds its particular utility in a construction of transformers of large size. It has to do primarily with the tapping arrangements of the transformer.

The general object of the invention is the provision of aconstruction wh ch affords a desired variety of tappings in minimum space, and wherein possible injurious effects, incident to the use of the difli'erent tappings, are avoided.

One of the specific objects of the invention is a construction which will avoid the creation of circulating currents in connected secondary coils of the transformer, or minirnize their heating efi'ects.

Other objects will be pointed out or indicated hereinafter, or be obvious to one skilled in the art, upon an understanding of the present disclosure.

In the drawin forming a part of this specification I il ustrate diagrammatically various arrangements in accor ance with the invention, but it is intended that the appended claims cover all other and different arrangements falling within the true and most comprehensive scope of the invention .in the art. In the drawing,

Fig. 1 is a diagram of a usual tapping arrangement employed in transformers having parallel connected secondary branches,

Fig. 2 is a diagram illustrating one arraigement contemplated by the invention, an

Figs. 3 to 6 inclusive are diagrams illustratin other arrangements in accordance with t e invention. I

Referrin to these illustrative arrangements, let it be understood that in each mstance a designates the rimary of the transformer and band a ranches of the secondary winding, which are connected in parallel at their ends. According to a tapping arrangement quite generally employed, tappings such as d, e and f are connected with corresponding portions of the windings b and c, as by conductors i and k, thus forming inter-connections between the branches at the tappin points. As a result, an instant current ow, when the tapping e is in use, will be as indicated by the arrows in Fig. 1, the portions 'marked 0 being without current if the inductive effects in the two ranches a and b are exactly uniform. As mathematical uniformity is not usually attamed in commercial manufacture, however, the working portions of the two branches will not have exactly the same Volta e, and as a result circulating currents will e roduced, having undesirable heating e acts and affecting the efliciency of the transformer. In an arrangement contemplated by my invention, the secondary branches 6 and c are not cross-connected at the taps, the respective tappings having connection only with respective branches, as illustrated by the arrangement of the tappin e and f in Fig. 2, both connected to t e branch 0 only, or by the arrangement shown in Fig. 3, wherein the tappings g and h are both connected to branch I) only and arranged alternately with toppings e and f. The arrows in F1 2 indicate the instant current flow with t e tapping e in use, and in Fig. 3 with the tapping g in use.

By such arrangements the creation of circulating currents between the parallel connected secondary branches is avoided, or their heating efi'ects minimized, and a desired variety of tappings is afforded without necessitating interconnections of the branches, which are troublesome in manufacture and require a substantial amount of space. Furthermore, with this arrangement of toppings, more of them may be provided in a given space than with the previous arrangement, and thus a greater number of voltages rendered availab The invention may be utilized in conjunction with an interconnected tapping, as illustrated in Fig. 4, when it may be desired to minimize the copper losses incident to use of the lower voltage tapping. In this diagram the tapping is interconnected with the branches 1) an a through the con nection m, and the single branch tappings e and p are arranged at the higher voltage side of the tapping f, the latter being sufliciently removed from the end connection (1 to interpose between them an amount of the windings sufiicient to dissipate .the heating effect of circulating currents resulting from the diflerence' in voltage between the active portions of the branch If it is desired to provide more than two parallel connected branches with taps according to the invention, the part n of the tapped branch 1) (Fig. 5), which is heavily loaded by the sum of the currents of the branches 1) and 0, ma be given a larger copper cross-section. I or tapping of a still larger number of branches, such as the four branches 6, a, p and g shown in Fig. 6, the branches may be connected up into equal groups by the customary cross-connections, and the groups tapped separately. As shown in said figure, one group is comprised of the branches 1) and p, which'are cross-connected by the connection I: and have the tapping F, the other group comprising the branches 0 and g having the cross-connection z" and the tapping e What- I claim is:

1. Transformer construction comprising secondary branch windings of the same phase connected in parallel at their ends, with tappings on respective branches, the tappings on one branch being insulated from the point of the potential on the other branch.

2. Transformer construction comprising secondary branch windings of the same phase connected in parallel at their ends and with tappings all on the same branch.

3. Transformer construction comprising secondary branch windings connected in parallel at their ends and having intermediate tappings, the tappings on one branch being insulated from the tappings on the other branch.

4. A transformer comprising a pair of parallel windings of the same phase connected at their ends, and intermediate tappings on one of said windings, said tappings being insulated from the points of correspending potential on the other of said windings.

5. A transformer comprising a pair of parallel windings of the same phase connected at their ends, a set of intermediate tappiugs on one of said windings, and a. set. of intermediate tappings on the other of said windings insulated from the tappings of the first set.

6. A transformr comprising a pair of parallel windings of the same phase connected at their ends, a set of intermediate tappings on one of said windings, and a set of intermediate tappings on the other of said windings insulated from the tappings of the first set, the tappings of one set being of a difierent potential than the tap pings of the other set.

7. A transformer comprising a pair of parallel windings of the same phase connected at their ends, a set of intermediate tappings on one of said windings insulated from the points of corresponding potential on the other of said windings, and an additional set of tappings connecting points of corresponding potential on both of said windings.

8. In a transformer, a plurality of branch windings of the same phase connected in parallel at their ends, and a plurality of intermediate tappings of different voltages on said windings, successive tappings being on difi'erent branches of said windings, the tappings of one potential on one of said branches being insulated from a point of corresponding potential on another of said branches.

In testimony whereof I have hereunto subscribed my name at Zurich, Switzerland on the 3rd day of February A. D. 1926.

JOSEF FISCHER. 

